The present invention relates generally to heat-transfer labels and more particularly to a heat-transfer label including a phenoxy adhesive layer.
Heat-transfer labels are commonly used in the decorating and/or labelling of commercial articles, such as, and without limitation to, containers for beverages (including alcoholic beverages, such as beer), essential oils, detergents, adverse chemicals, as well as health and beauty aids. As can readily be appreciated, heat-transfer labels are desirably resistant to abrasion and chemical effects in order to avoid a loss of label information and desirably possess good adhesion to the articles to which they are affixed.
One of the earliest types of heat-transfer label is described in U.S. Pat. No. 3,616,015, inventor Kingston, which issued October, 1971, and which is incorporated herein by reference. In the aforementioned patent, there is disclosed a heat-transfer label comprising a paper sheet or web, a wax release layer affixed to the paper sheet, and an ink design layer printed on the wax release layer. In the heat-transfer labelling process, the label-carrying web is subjected to heat, and the label is pressed onto an article with the ink design layer making direct contact with the article. As the paper sheet is subjected to heat, the wax layer begins to melt so that the paper sheet can be released from the ink design layer, a portion of the wax layer being transferred with the ink design layer and a portion of the wax layer remaining with the paper sheet. After transfer of the design to the article, the paper sheet is immediately removed, leaving the design firmly affixed to the article and the wax transferred therewith exposed to the environment. The wax layer is thus intended to serve two purposes: (1) to provide release of the ink design from the web upon application of heat to the web and (2) to form a protective layer over the transferred ink design. After transfer of the label to the article, the transferred wax release layer is typically subjected to a post-flaming technique which enhances the optical clarity of the wax protective layer (thereby enabling the ink design layer therebeneath to be better observed) and which enhances the protective properties of the transferred wax release.
Many heat-transfer labels include, in addition to the layers described above, an adhesive layer (comprising, for example, a polyamide or polyester adhesive) deposited over the ink design to facilitate adhesion of the label onto a receiving article. An example of a heat-transfer label having an adhesive layer is disclosed in U.S. Pat. No. 4,548,857, inventor Galante, which issued Oct. 22, 1985, and which is incorporated herein by reference. Additionally, many heat-transfer labels additionally include a protective lacquer layer interposed between the wax release layer and the ink layer. An example of such a label is disclosed in U.S. Pat. No. 4,426,422, inventor Daniels, which issued Jan. 17, 1984, and which is incorporated herein by reference.
One phenomenon that has been noted with heat-transfer labels of the type described above containing a wax release layer is that, quite often, a degree of hazing or a "halo" is noticeable over the transferred label when the transfer is made onto clear materials. This "halo" effect, which persists despite post-flaming and which may detract from the appearance of the label, is caused by the wax coating around the outer borders of the transferred ink design layer. Hazing due to the wax release layer may also appear in "open-copy" areas of the label, i.e., areas of the label where no ink is present between the adhesive and protective lacquer layers, and also may detract from the appearance of the label.
In addition to and related to the aforementioned problem of hazing, when heat-transfer labels of the type described above are applied to dark-colored containers, the outer wax layer of the label often appears as a whitish coating on the container, which effect is undesirable in many instances. Furthermore, scratches and similar abrasions to the outer wax layer of the label can occur easily and are readily detectable.
Accordingly, to address the aforementioned issues, considerable effort has been expended in replacing or obviating the need for a wax release layer. One such wax-less, heat-transfer label is disclosed in U.S. Pat. No. 3,922,435, inventor Asnes, which issued Nov. 25, 1975, and which is incorporated herein by reference. In the aforementioned patent, the layer of wax is replaced with a layer of a non-wax resin. This non-wax resinous layer is referred to in the patent as a dry release since it does not transfer to the article along with the ink design layer. In a preferred embodiment of the patent, the non-wax resinous layer comprises a thermoset polymeric resin, such as cross-linked resins selected from the group consisting of acrylic resins, polyamide resins, polyester resins, vinyl resins and epoxy resins.
Another example of a wax-less, heat-transfer label is disclosed in U.S. Pat. No. 4,935,300, inventors Parker et al., which issued Jun. 19, 1990, and which is incorporated herein by reference. In the aforementioned patent, the label, which is said to be particularly well-suited for use on high density polyethylene, polypropylene, polystyrene, polyvinylchloride and polyethylene terephthalate surfaces or containers, comprises a paper carrier web which is overcoated with a layer of polyethylene. A protective lacquer layer comprising a polyester resin and a relatively small amount of a nondrying oil is printed onto the polyethylene layer. An ink design layer comprising a resinous binder base selected from the group consisting of polyvinylchloride, acrylics, polyamides and nitrocellulose is then printed onto the protective lacquer layer. A heat-activatable adhesive layer comprising a thermoplastic polyamide adhesive is then printed onto the ink design layer.
Although the above-described wax-less, heat-transfer label substantially reduces the wax-related effects discussed previously, said label does not quite possess the same release characteristics of heat-transfer labels containing a wax release layer. Accordingly, another type of heat-transfer label differs from the heat-transfer label disclosed in U.S. Pat. No. 4,935,300, only in that a very thin layer or "skim coat" of a waxlike material is interposed between the polyethylene release layer and the protective lacquer layer to improve the release of the protective lacquer from the polyethylene-coated carrier web. The thickness of the skim coat corresponds to approximately 0.1-0.4 lbs. of the waxlike material spread onto about 3000 square feet of the polyethylene release layer.
An example of the aforementioned type of heat-transfer label, which has been sold by the assignee of the present application for use in labelling polypropylene bottle caps, comprises a paper carrier web overcoated with a layer of polyethylene. A skim coat is overcoated on the polyethylene layer. A protective lacquer layer comprising vinyl and polyester resins is printed onto the skim coat. An ink design layer comprising vinyl and polyester resins is printed onto the protective lacquer layer. A heat-activatable adhesive layer comprising an acrylic resin, a solvent-soluble chlorinated polypropylene and a plasticizer is printed over the ink design and protective lacquer layers. The acrylic resin is a butyl methacrylate resin, such as ELVACITE.RTM. 2045, which is commercially available from ICI Acrylics Inc. (Wilmington, Del.). The solvent-soluble chlorinated polypropylene is commercially available from Eastman Chemical Products, Inc. (Kingsport, Tenn.) as chlorinated polyolefin CP-343-1. The plasticizer is a glyceryl tribenzoate, such as BENZOFLEX.RTM. S-404, which is commercially available from Velsicol Chemical Corporation (Chicago, Ill.).
In U.S. Pat. No. 5,824,176, inventors Stein et al., which issued Oct. 20, 1998, and which is herein incorporated by reference, there is disclosed a composition for use in forming an adhesive layer and a heat-transfer label including such an adhesive layer. In one embodiment, the label is designed for use on silane-treated glass containers of the type that are subjected to pasteurization conditions. The label includes a support portion and a transfer portion, the transfer portion being positioned over the support portion. The support portion includes a sheet of paper overcoated with a release layer of polyethylene. The transfer portion includes an organic solvent-soluble phenoxy protective lacquer layer, an organic solvent-soluble polyester ink layer over the protective lacquer layer, and an acrylic adhesive layer over the ink layer. The adhesive layer is formed by depositing onto the ink layer, e.g., by gravure printing, a composition comprising a water-based acrylic resin dispersion or emulsion, isopropyl alcohol and water, and then evaporating the volatile components of the composition to leave an acrylic film.
In U.S. Pat. No. 5,800,656, inventors Geurtsen et al., which issued Sep. 1, 1998, and which is incorporated herein by reference, there is disclosed a heat-transfer label including a phenoxy lacquer layer. In one embodiment, the label is designed for use on silane-treated glass containers of the type that are subjected to pasteurization conditions. The label includes a support portion and a transfer portion, the transfer portion being positioned over the support portion. The support portion includes a sheet of paper overcoated with a release layer of polyethylene. The transfer portion includes an organic solvent-soluble phenoxy resin protective lacquer layer, an organic solvent-soluble polyester resin ink layer over the protective lacquer layer, and a water-dispersible acrylic adhesive resin layer over the ink layer.
In commonly-assigned, presently-pending U.S. patent application Ser. No. 09/093,150, which application is incorporated herein by reference, there is disclosed a heat-transfer label suitable for use in decorating glass articles. According to one embodiment, the label is capable of withstanding pasteurization conditions and includes (a) a support portion in the form of a sheet of paper overcoated with a release layer of polyethylene, (b) a skim coat of wax overcoated onto the polyethylene release layer and (c) a transfer portion, the transfer portion including a cross-linked phenoxy protective lacquer layer printed onto the skim coat, a polyester ink layer printed onto the protective lacquer layer, and a first adhesive layer printed onto the ink layer and onto any exposed portions of the underlying protective lacquer layer. The aforementioned cross-linked phenoxy resin comprises a solvent-soluble phenoxy resin of the formula ##STR2## wherein said solvent-soluble phenoxy resin is cross-linked by a partially methylated melamine formaldehyde resin. The above-mentioned first adhesive layer comprises an acrylic adhesive resin of the type present in a water-based adhesive dispersion or in a water-based adhesive emulsion (e.g., RHOPLEX.RTM. GL-618 emulsion) and also comprises an alcohol, a pH adjustment agent for bring the pH of the adhesive composition to about 9-10 and a surfactant in the form of dioctyl sodium sulfosuccinate (e.g., Triton GR-5M).
The aforementioned label has been used to decorate silane-treated glass containers and, by and large, has proven to be generally satisfactory in terms of scuff resistance and ability to withstand pasteurization conditions (for example, where the glass containers are used to hold beer that is pasteurized in the glass containers). Nevertheless, the present inventors have noted that, when used to label thick-walled, silane-treated glass containers, such as wine bottles or other heavy glass bottles, the subject label often has a tendency to become scuffed or damaged by bottle-to-bottle or bottle-to-machinery contact during filling, packaging and/or shipping operations. Accordingly, there exists a need for a label that is well-suited for use on silane-treated glass containers, that exhibits improved scuff resistance and that can withstand pasteurization conditions.
Other patents and publications of interest relating to the use of heat-transfer labels include U.S. Pat. No. 4,927,709, inventors Parker et al., which issued May 22, 1990; and PCT Application No. PCT/US97/11309, published Jan. 8, 1998, both of which are incorporated herein by reference.